This invention relates to cabs for tractors and, more particularly, to such cabs which are to close an operator platform and are mounted on a rollover operator protection structure. Representative prior art includes Babbit U.S. Pat. No. 3,632,134 and Moore U.S. Pat. Nos. 3,572,819 and 3,623,754.
The desire to protect the operator of tractors working in rugged environments from both noise and injury due to the overturning of the tractor has resulted in the extensive use of rollover operator protection structures enclosing cabs for the operator platform on the tractor. Typically, the cab will be formed of sheet metal material and secured at its upper end to upper portions of the rollover operator protection structure. In one construction such as that shown in Moore U.S. Pat. No. 3,572,819, the lower end of the cab sealingly cooperates with the operator platform by means of wiper-like seals depending from the lower edges of the side walls of the cabs and engaging the upper surface of the operator platform.
The rollover operator protection structure, of course, prevents injury to the operator in the event the tractor overturns while sealing means results in the cab being sealed from the exterior against noise generated by the tractor motor. The lack of securing means securing the lower end of the cab to the operator platform minimizes the transmission of vibration to the interior of the cab.
However, when the tractor is operating in rugged terrain, the side walls of the cab tend to shift fore and aft and side to side relative to the operator platform with the result that the seal will not be universally maintained, the sealing elements are subject to excessive wear; and when the shifting is excessively severe, the usual means by which the upper end of the cab is secured to the rollover operator protection structure, frequently welds, become overstressed and fail.
On the other hand, where the cab side walls are connected directly to the platform, the noise level within the cab is frequently increased due to resonant vibration of the fixed but relatively flexible sheet metal walls of the cab. Moreover, such cabs tend to provide assembly problems on assembly lines in that the various components, by reason of their being firmly fixed to each other and to the tractor structure, must be made with more precise tolerances than is required in the manufacturing of cabs according to the above identified Moore patent.